When a friend is violently killed after thrusting three musical cassettes into Jonathan Derry's hands, the young physician is hurled headlong into a terrifying nightmare. It turns out that these seemingly harmless tapes contain a computerized horse-betting system that could make whoever possesses them a very rich man-or a very dead one. Now Jonathan must track down the tape's rightful owners before the odds of him outrunning a cold-blooded killer become slim to none...